Ecological Assessment of Coral

Palmyra Atoll, NOAA photo by Erin Looney.

Corals are the defining species in one of the most diverse marine ecosystems: coral reefs. The Coral Reef Ecosystem Division (CRED)
studies of corals focus on basic questions concerning the distribution, abundance, and condition of corals and coral reefs in selected
areas across the tropical and subtropical Pacific under U.S. jurisdiction.

CRED studies address the following questions:

What are the diversity and relative abundance of corals?

How can the habitats in which corals occur be qualitatively and quantitatively analyzed?

What is the spatial distribution of habitats in which corals occur?

What is the capacity of corals to replenish populations over space and time?

Coral percent cover data are important not only because percent cover is the most widely used metric of coral reef condition but also
because changes in cover likely reflect the set of environmental and disturbance regimes that characterize each reef system (Rogers et
al. 1994; Jokiel et al. 2005).

Rose Atoll. NOAA photo by Erin Looney.

Marine biodiversity is predicted to be indirectly affected by climate change and ocean acidification (Worm et al. 2006; Riebesell 2008)
because of the implicit alterations in community structure, synergism among organisms, and functionality and the anticipated increases
in species extinctions and invasion (Ives and Carpenter 2007; Cheung et al. 2009). Coral reefs, change greatly in diversity and
community composition across spatial and environmental gradients. Although the details of how this variation influences reef resilience
and response to climate change and ocean acidification are poorly understood, ecological resilience is generally considered to be
enhanced by increased activity.

Size-class distribution, or coral demographics, is important because it can serve as a telling indicator of disturbance on a reef. For
example, a distribution in which an abundance of corals occur within large size classes (>50 cm) suggests a region in which disturbance
events have not interfered with the growth of corals over long periods of time. Conversely, a distribution in which the majority of
corals occur within small size classes (<10 cm) suggests either a recent, severe disturbance or frequent recurrences of moderate
disturbance, after which recruitment and growth have been relatively recent processes. Other factors to consider when interpreting the
implications of size-class distribution include species-specific life history strategies and environmental regimes to which corals are
exposed (e.g., frequent high-energy waves). Recruitment of juvenile corals also is an important measure obtained from size-class
distribution data.